Games:

Algebra
Function Tables
Algebra Expressions
4th Grade Algebra
Order of Operations
Another Order of Operations (choose medium or hard)
Practice Algebra problems

Multiplication and Division
Interactive Multiplication Chart
Multiplication Chart Self-Quiz
Multiplication Games
Multiplication Facts Games
Division Games

Coins
Coin Box Interactive Game
Measurement Games

Geometry Games
http://www.math-play.com/3d-shapes.html
http://www.factmonster.com/math/knowledgebox/player.html?movie=sfw41448
http://www.harcourtschool.com/activity/mmath/mmath_dr_gee.html

General
Interactive Games

Language Arts Games
Fourth Grade Literacy
Third Grade Literacy
Third Grade Comprehension
Vocabulary Games
Grammar

Unit Study Games
Science Games
Science Games
Weather Games
Space Games
Astronomy Games
Types of Matter Games

Math Vocabulary Websites
A Maths Dictionary for Kids